1. Field of Invention
The present invention relates to a heat exchange device of a perforated plate exchanger type with improved sealing.
2. Description of the Prior Art
For some time, so-called "compact" exchangers have been proposed formed of stacks of perforated plates, in which the perforations are disposed so that stacking thereof creates separate spaces in which the fluids (liquids, gases or smoke) taking part in the heat exchange may flow.
The applicant has himself described devices of this type, in particular in the French Pat. No. 2455721 "Compact heat exchanger" and the French patent application No. 2500610 "Perforated plate heat exchanger".
Depending on the arrangement of the perforations on the plates and the arrangement of the plates in the stack forming the exchanger, the fluid flow spaces may consist of channels whose direction is perpendicular to the plane of the plates or "flow networks" created by interconnection of perforations between the adjacent plates of the stack.
In all cases, the flow spaces through which the fluids taking part in the heat exchange travel (assemblies of channels or networks of interconnected perforations) must be separated from the adjacent flow spaces through which flow another fluid so as to reduce as much as possible leaks between the different flow spaces through which different fluids pass. To obtain this result, it would be necessary to use perforated plates of very good inherent flatness having a good surface condition, very tightly clamped against each other.
Obtaining improved flatness and surface condition for the perforated plates forms a restriction which may lead to considerable increase of the complexity and of the cost of their fabrication. Since the desired sealing further requires considerable clamping of the stack, it would be necessary to use means such as flanges of sufficient thickness on each side of the stack (which would make the assembly considerably much heavier), as well as tie-rods in sufficient number and quality for reducing the internal leaks to a value compatible with the desired operation of the device. There would also follow an increase in the complexity and cost of mounting exchangers of this type.
Under these conditions, it was particularly important to efficiently overcome the problem raised and it has occured to turn to the use of joints, disposed alternately with all the plates of the stack. Now, the constructional characteristics of compact exchangers and particularly the pressure to be exerted for maintaining cohesion of the stack are such that it is particularly difficult to select a material adapted for the contemplated use.
Now, it has been discovered recently that, among the very large number of materials which could be contemplated for this use, certain expanded graphites such as defined further on offer an assembly of properties which make them particularly well adapted to this use.
The main object of this invention is to provide a plate heat exchanger which, in addition to the advantages of low cost, compactness, relative lightness and ease in distributing the fluids, does not have any leaks or has negligible leaks between the fluids between which the heat exchange is to take place.